Ion implantation is a standard technique for introducing impurities into semiconductor wafers. A desired impurity material may be ionized in an ion source, the ions may be accelerated to form an ion beam of prescribed energy, and the ion beam may be directed at a front surface of the wafer. The energetic ions in the beam penetrate into the bulk of the semiconductor material and are embedded into the crystalline lattice of the semiconductor material. The ion beam may be distributed over the wafer area by beam movement, by wafer movement, or by a combination of beam and wafer movement.
An ion implanter may have a terminal structure. The terminal structure may sometimes be referred to in the art as a “terminal” or “high voltage terminal” and is fabricated of conductive material such as metal. The terminal structure may have varying geometries that define a cavity and the ion source is at least partially disposed within the cavity. The terminal structure may be energized to a terminal voltage to assist with acceleration of the ions from the ion source. The terminal structure, as well as other components and sub-systems of the ion implanter, are typically surrounded by a grounded enclosure. The grounded enclosure thus protects personnel from high voltage dangers when the ion implanter is running and protects the components and sub-systems of the ion implanter.
Air has conventionally been used to insulate the terminal structure from the grounded enclosure. However, there is a constraint on the distance of the air gap between the terminal structure and the grounded enclosure since the size of the grounded enclosure is limited in the volume manufacturing of semiconductors. Accordingly, most conventional ion implanters have limited the voltage of the terminal structure to about 200 kV.
Accordingly, there is a need in the art for a terminal structure of an ion implanter capable of modifying an electric field about the terminal structure in order to energize the terminal structure to high voltages within a reasonably sized enclosure footprint.